A known approach to cleanspace-assisted fabrication of materials such as semi-conductor substrates, is to assemble a manufacturing facility as a “cleanroom.” In such cleanrooms, processing tools are arranged to provide aisle space for human operators or automation equipment. Exemplary cleanroom design is described in: “Cleanroom Design, Second Edition,” edited by W. Whyte, published by John Wiley & Sons, 1999, ISBN 0-471-94204-9, (herein after referred to as “the Whyte text”.
Cleanroom design has evolved over time to include locating processing stations within clean hoods. Vertical unidirectional air flow can be directed through a raised floor, with separate cores for the tools and aisles. It is also known to have specialized mini-environments which surround only a processing tool for added space cleanliness. Another known approach includes the “ballroom” approach, wherein tools, operators and automation all reside in the same cleanroom.
Evolutionary improvements have enabled higher yields and the production of devices with smaller geometries. However, known cleanroom design has disadvantages and limitations.
For example, as the size of tools has increased and the dimensions of cleanrooms have increased, the volume of cleanspace that is controlled has concomitantly increased. As a result, the cost of building the cleanspace, and the cost of maintaining the cleanliness of such cleanspace, has increased considerably.
Tool installation in a cleanroom can be difficult. The initial “fit up” of a “fab” with tools, when the floor space is relatively empty, can be relatively straight forward. However, as tools are put in place and a fab begins to process substrates, it can become increasingly difficult and disruptive of job flow, to either place new tools or remove old ones. It would be desirable therefore to reduce installation difficulties attendant to dense tool placement while still maintaining such density, since denser tool placement otherwise affords substantial economic advantages relating to cleanroom construction and maintenance.
Another area of evolutionary improvement has come with improvements in robotics. Substrate processing has changed from a manually intensive process where human operators handled substrates or batches of substrates. In current cleanroom designs, many processing tools include robotics for substrate handling. In some fabricator settings, human interaction is reduced to: loading collections of substrates onto processing tools, unloading collections of substrates from processing tools and moving collections of substrates from one processing tool to another. Evolutionary advances have transitioned into cleanroom robotics which are extremely complex and therefore costly and error prone.
In some cases, in a modem semiconductor fabricator, substrates move from tool to tool in specialized carriers which contain multiple substrates. The carriers interface with appropriate automation to allow for movement of the substrates around the fab and for loading and unloading the substrates from a processing tool.
The size of substrate has increased over time as have the typical sizes of fabs. The increased size allows for economies of scale in production, but also creates economic barriers to development and new entries into the industry. A similar factor is that the processing of substrates is coordinated and controlled by batching up a number of substrates into a single processing lot. A single lot can include, for example, 25 substrates. Accordingly, known carriers are sized to typically accommodate the largest size lot that is processed in a fab.
It would be desirable to have manufacturing facilities for cleanspace-assisted fabrication, that use less cleanspace area, permit dense tool placement while maintaining ease of installation, which permit the use of more simple robotics and which are capable of efficiently processing a single substrate.